TY - JOUR
T1 - Astrochronology of the Ediacaran Shuram carbon isotope excursion, Oman
AU - Gong, Zheng
AU - Li, Mingsong
N1 - Funding Information:
Zheng Gong was supported by the Graduate Student Fellowship from Yale University . Mingsong Li was supported by the Heising-Simons Foundation , United States ( 2016–11 ). We thank Moujahed Al-Husseini and GeoArabia for permission to use the data, Lei Xu for data collection, and David Evans, Alan Rooney, and Ross Mitchell for helpful discussions. Critiques from the editor and two reviewers led to an improved manuscript.
Publisher Copyright:
© 2020 Elsevier B.V.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - The Ediacaran is a highly dynamic period in terms of large perturbations in Earth's atmosphere, biosphere, and climate. Among these perturbations, a pronounced negative carbon isotope excursion, known as the Shuram excursion (SE), is characterized by the most depleted δ13C values (-12‰) that have ever been observed in the geological record. A poorly determined chronostratigraphic framework makes the SE difficult to correlate and compare globally. Therefore, it is hard to study the potential connection between the SE and coeval climate and biological variations. Here, we present a high-resolution astrochronological study of the Ediacaran Shuram and Buah Formations, Nafun Group, Oman, in which the SE is reported for the first time. Power spectral analysis of the 600-m long gamma ray log of the Miqrat-1 Well shows that a hierarchy of astronomically-forced climate cycles (eccentricity, obliquity, and precession) is accurately-preserved. Using multiple statistical tests, we constructed a sedimentation rate variation profile that covers the entire SE, which is characterized by low rates in shale-dominated layers and high rates in shale-carbonate interbedded layers. The duration of the SE in Oman is suggested to be 7.7 ± 0.2 Myr, which agrees with estimates from South Australia, South China, and the United States. An identical duration of the SE supports its global synchroneity and indicates a primary origin of the depleted δ13C values. Combined with the newly proposed termination age (562.5 ± 1.1 Ma) of the SE, our astrochronological results suggest that the onset age of the excursion is 570.2 ± 1.1 Ma. The astrochronology of the SE delineates the tempo of the excursion, with a rapid decrease (∼ 1 Myr) from the onset to its isotopic nadir followed by a more gradual recovery (∼ 6–7 Myr) towards the termination. The new chronostratigraphic framework permits further investigations of the potential causal links between the global carbon cycle and the widespread glaciation, the oceanic oxygenation, and the biological diversification in Ediacaran time.
AB - The Ediacaran is a highly dynamic period in terms of large perturbations in Earth's atmosphere, biosphere, and climate. Among these perturbations, a pronounced negative carbon isotope excursion, known as the Shuram excursion (SE), is characterized by the most depleted δ13C values (-12‰) that have ever been observed in the geological record. A poorly determined chronostratigraphic framework makes the SE difficult to correlate and compare globally. Therefore, it is hard to study the potential connection between the SE and coeval climate and biological variations. Here, we present a high-resolution astrochronological study of the Ediacaran Shuram and Buah Formations, Nafun Group, Oman, in which the SE is reported for the first time. Power spectral analysis of the 600-m long gamma ray log of the Miqrat-1 Well shows that a hierarchy of astronomically-forced climate cycles (eccentricity, obliquity, and precession) is accurately-preserved. Using multiple statistical tests, we constructed a sedimentation rate variation profile that covers the entire SE, which is characterized by low rates in shale-dominated layers and high rates in shale-carbonate interbedded layers. The duration of the SE in Oman is suggested to be 7.7 ± 0.2 Myr, which agrees with estimates from South Australia, South China, and the United States. An identical duration of the SE supports its global synchroneity and indicates a primary origin of the depleted δ13C values. Combined with the newly proposed termination age (562.5 ± 1.1 Ma) of the SE, our astrochronological results suggest that the onset age of the excursion is 570.2 ± 1.1 Ma. The astrochronology of the SE delineates the tempo of the excursion, with a rapid decrease (∼ 1 Myr) from the onset to its isotopic nadir followed by a more gradual recovery (∼ 6–7 Myr) towards the termination. The new chronostratigraphic framework permits further investigations of the potential causal links between the global carbon cycle and the widespread glaciation, the oceanic oxygenation, and the biological diversification in Ediacaran time.
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U2 - 10.1016/j.epsl.2020.116462
DO - 10.1016/j.epsl.2020.116462
M3 - Article
AN - SCOPUS:85088637199
SN - 0012-821X
VL - 547
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
M1 - 116462
ER -
